By the nitrogen isotope method and investigation of the land use in the study area, twenty-one wells were sampled to identify the groundwater quality in urban area, Hangzhou City. The result showed that nitrate pollution of the groundwater was serious. The groundwater fell into the water category of Grade Ⅲ in terms of quality and was not potable. There was a high frequency of the samples (40.5% of the total) with nitrate above WHO's standards of N 10 mg L^-1 for NO₃-N. Areas different in land use areas were also different in nitrate concentrations (ranging between N 0.04~34.41 mg L^-1) and δ¹⁵N NO₃ values (between 7.8‰~35.5‰) of the groundwater. At the same time the nitrogen isotope method to investigate nitrate sources: in residential areas D15 N NO₃ was 10.4‰~22.0‰, and in agricultural area 17.5‰~19.5‰. Domestic sewage was the major nitrate source to the shallow groundwater in the urban area, septic tank still existing in the residential, settings the point sources of nitrate, and manure application in the agricultural areas, the non-point sources of NO₃-N sources pollution.